Effect of α+β phase rolling and aging treatment on laminated bimodal structure in high temperature titanium alloy

Abstract

In this work, we have prepared a novel laminated bimodal structure with layer-by-layer distribution of αp and αs phase in high temperature titanium alloy by α+β phase rolling and aging treatment. The lamellar bimodal microstructure is comprised of long-primary αp and secondary αs phase in the Ti-6.0Al-3Sn-5Zr-0.5Mo-1.0Nb-1.0Ta-0.4Si-0.2Er alloy. During α+β phase rolling at 990 °C, the primary αp grain deformed to elongated layer structure, while the lamella secondary αs deformed to kinked and broken chaos morphology. After 800 °C for 1h stabilization and 700 °C for 5h aging treatment, the thickness of the elongated αp layer slightly grew, while the kinked and broken αs were recovered and partially recrystallized to form a layered fine grain structure. The lamellar bimodal microstructure, i.e., elongated primary αp with layered bimodal αs phase has enhanced strength and ductility of the high temperature titanium alloy. This enhanced strength and toughness is mainly attributed to the lamellae αp structure and layered fine αs grain formed by hot rolling and aging treatment.